power trim

Power trim started working slow coming up. It went down at normal speed. I opened plug and fluid looked white and watery. Put new ATF in and lifted up and down bunch of times to remove air. It worked great for 6-7 times in yard and thought it was fine. Let boat sit for a couple months and now it will not go up or down. Batteries are charged and everything else is working fine. Did it have water and leak? Fluid is milky again. Motor had been left in down position.